[Ocfs2-users] Cluster Size

[Joel Becker]

On Wed, Oct 05, 2005 at 03:57:55PM -0400, Ralph Armstrong wrote:
> I am guessing it is an allocation size (i.e. how much space gets allocated
> at one time), but that is just my guess.  Filesystem performance appears to

	That is correct.  A cluster is the minimum unit of allocation.

> improve with a larger cluster size set, suggesting that setting a larger
> cluster size causes few locks on the filesystem during a write.

	It's not so much about locking, really.  Allocation of one
cluster comes from a node-local allocator.  It's about repetition.
	Note that "performance appears to improve" is only true with
regard to simple allocation.  The reduced granularity of larger cluster
sizes can have negative impacts on many workloads that involve small
files.
	Basically, tune your clustersize to your workload.

Joel

-- 

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Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker at oracle.com
Phone: (650) 506-8127